The Few centuries ago building construction within major cities such as New York, London and Tokyo was completed by using bricks and mortar only, as there were no lift elevators it was not feasible or possible to build higher than a certain point.
In the late 1800's, new civil engineering methods and technology redefined limits for high rise construction. It became possible to build amazingly high towers. The advancement came with the advent of lift elevators and new steel manufacturing processes which produced long beams. Essentially, architects had a whole new set of building blocks to work with, as relatively narrow, lightweight steel beams could support much more weight than older solid brick constructed buildings limited to height of about ten stories.
Engineers and architects understood that the central support structure of high rise buildings or skyscrapers would have to comprise of both concrete and steel. From the late 1900's till this date high rise buildings have been built using a standard concept of lifting individual steel beam girders by tower cranes delivered to workers assembling them together at each floor level in a vertical and horizontal arrangement. The process is labour intensive and is very slow. A major challenge that high rise construction contractors have to contend with is the factor of ‘time’. If a project is not completed by scheduled dates, then huge fines can be imposed and the cost of construction can soar.
The current construction method used to build skyscrapers is to first elevate a central core wall constructed of steel rebar and reinforced concrete. After the core wall has reached a height of approximately ten floors, workers begin to assemble an outer embracing frame of structural steel. The inner concrete core wall is essentially the only part of current day elevated construction. The inner concrete core wall is built from the ground level upwards with a construction lapping zone between the core wall height and the outer embracing steel frame. The inner core wall actually accommodates the most innovative part of the whole process in elevation, it is the hydraulically powered tower crane deck, elevated to a higher level each time the wall is constructed further upwards.
The inner concrete core wall is constructed by simply erecting eight individual steel wall templates and placing a steel rebar cage inside, essentially the steel rebar cage is sandwiched in-between the steel wall templates. Reinforced concrete is then poured inside. After the concrete has settled and hardened, the steel wall templates are removed and shifted upwards to continue the construction of another level. Internal rails are then added bellow on the newly constructed walls allowing the entire tower crane deck to be elevated hydraulically upwards.
The inner concrete core wall is continually constructed and elevated vertically upwards until the complete structure has reached its desired level of height. The inner concrete core wall is built with a higher construction lapping zone than the outer embracing steel frame structure of approximately ten floors. The height discrepancy is maintained throughout the tower construction, as the tower crane deck requires a height advantage in-order to lift the long girder beams from the ground level delivering them upwards to workers assembling them together at each level as an outer-embracing steel frame structure.
The inner concrete core wall also acts as central support structure of the complete constructed building. The outer embraced structural steel frame of vertical and horizontal steel girder beams are secured into the inner core wall, thereby supporting the constructed buildings flexible swaying movements in high winds.